Polymers and Plastics Technology Handbook

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Polymers and Plastics Technology Handbook

Author: NIIR Board
Format: Paperback
ISBN: 8178330768
Code: NI84
Pages: 424
Price: Rs. 750.00   US$ 100.00

Published: 2004
Publisher: Asia Pacific Business Press Inc.
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Plastics play a very important role in our daily lives. Throughout the world the demand for plastic, particularly plastic packaging, continues to rapidly grow. Polymer technology deals with the manufacture and production of polymer and synthetic substances. Plastic is incredibly versatile and can be made from different ingredients, moulded into any shape, and put to a huge range of uses across industry and the rest of society, from carrier bags to electrical cables. Polymer energy system is an award winning, innovative, proprietary process to convert waste plastics into renewable energy. Some of the important example of polymers and plastics are polytetra fluoroethylene (PTFE), polyether sulphone (PES), phenol-formaldehyde (PF), polyolefins, vinyl polymers, thermoplastic polyesters, polysulfones, poly(phenylene sulfide), etc. Polymers are the most rapidly growing sector of the materials industry. The Indian plastic industry has taken great strides. In the last few decades, the industry has grown to the status of a leading sector in the country with a sizable base. The material is gaining notable importance in different spheres of activity and the per capita consumption is increasing at a fast pace. Continuous advancements and developments in polymer technology, processing machineries, expertise, and cost effective manufacturing is fast replacing the typical materials in different segments with plastics. On the basis of value added, Indian share of plastic products industry is about 0.5% of national GDP.
The major contents of the book are properties and applications of speciality plastics, thermoset plastics, applications of recycle plastics, introduction of polymer science, polymer additives, blends and composites, commodity thermoplastics and fibres etc. This book also consists of raw material suppliers for plastic and plastic products, manufacturers of plastic, processing machinery, plastics processing machinery and equipment (foreign), machinery and equipment for plastic converting, extruders and extrusion lines, injection moulding machines, presses and accessories, blow moulding and thermoforming machines etc.
The book has been designed with the idea of blending and integrating basic polymer science and the technology of plastics into a composite structure. This book is an outcome of an endeavour in the direction of polymer and plastic processing. It would be of immense use to entrepreneurs, consultants, students and libraries etc.

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Contents

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1. PROPERTIES AND APPLICATIONS OF
SPECIALITY PLASTICS
Polytetra Fluoroethylene (PTFE)
Characteristics
Applications
Thermoplastic Polyurethanes (TPU)
Characteristics
Applications
Polysulphones (PSO)
Characteristics
Applications
Polyether Sulphone (PES)
Characteristics
Applications
Polyphenylene Sulphide (PPS)
Characteristics
Applications
Polyphenylene Ether (PPE)
Characteristics
Applications
Polyether Etherketone (Peek)
Characteristics
Applications
Polyarylates
Characteristics
Applications
Polyamide-Imide (PAI)
Characteristics
Applications
Polyether-Imide (PEI)
Characteristics
Applications
Liquid Crystal Polymers (LCP)
Characteristics
Applications
2. PROPERTIES AND APPLICATIONS OF
THERMOSET PLASTICS
Phenol-Formaldehyde (PF)
Characteristics
Applications
Amino Plastics
Characteristics
Applications
Melamine Formaldehyde
Urea Formaldehyde
Epoxy Resins
Characteristics
Applications
Unsaturated Polyester Resins
Characteristics
Applications
Polyurethane
Characteristics
Applications
Silicones
Silicone forms
Characteristics
Applications
Silicone fluids
Silicone Resins
Silicone Elastomers
3. APPLICATIONS OF RECYCLED PLASTICS
Introduction
Recycled LDPE
Recycled HDPE
Recycled Polypropylene
Recycled PVC
Recycled PS
Recycled PET
Recycled Commingled Plastics Waste
4. INTRODUCTION TO POLYMER SCIENCE
Classification of Polymers
Thermoplastics and Thermosets
Classification Based upon Polymerization Mechanism
Classification Based upon Polymer Structure
Polymer Structure
Copolymers
Tacticity
Geometric Isomerism
Nomenclature
Molecular-Weight Distribution
Molecular-Weight Averages
5. POLYMER ADDITIVES, BLENDS AND COMPOSITES
Additives
Plasticizers
Fillers and Reinforcements
Other Important Additives
Polymer Blends
Interpenetrating Networks
Mechanical Properties
Composite Fabrication
Reference
6. COMMODITY THERMOPLASTICS AND FIBERS
Thermoplastics
Polyolefins
Vinyl Polymers
Thermoplastic Polyesters
Fibers
Natural and Synthetic Fibers
Cellulose
Noncellulosics
Fiber-Spinning Operations
7. ENGINEERING AND SPECIALTY POLYMERS
Engineering Plastics
Polyamides
ABS
Polycarbonates
Modified Poly(phenylene oxide)
Acetal
Polysulfones
Poly(phenylene sulfide)
Engineering Polyesters
Fluoropolymers
Specialty Polymers
Polyimides and Related Specialty Polymers
Ionic Polymers
Polyaryletherketones
Specialty Polyolefins
Inorganic Polymers
Liquid-Crystal Polymers
Conductive Polymers
High-Performance Fibers
Other Specialty Polymers
8. POLYMER PROCESSING AND RHEOLOGY
Extrusion
Molding
Calendering
Coating
Non-Newtonian Flow
Viscosity of Polymer Solutions and Suspensions
Constitutive Equations
Elastic Properties of Polymeric Fluids
Pressure (Poiseuille) Flow
Drag Flow
Capillary Rheometer
Couette Rheometer
Cone-and-Plate Rheometer
Rheometric Characterization of Polymer Solutions and Melts
Introduction to the Modeling of Polymer-Processing
Operations: Extrusion
Appendices
9. COMPONENTS OF A THERMOPLASTIC
STRUCTURAL COMPOSITE
Thermoplastic Matrix Resins
Chain Extendable Resins
Amorphous Thermoplastics
Orientable Polymer Matrices
Semi-crystalline Thermoplastic Polymers
Polymer Blends and Compounds
The 'Victrex' Range of Aromatic Polymers
This allows for easy crystallization of the
polyetherketone family.
Polyetheretherketone
Reinforcing Fibres
Organic Polymeric Fibres
Inorganic Filaments
Carbon Fibres
High Strength Carbon Fibres
Interfaces and Interphases
Wetting of the Fibre by the Resin
Chemical Bonding
Mechanical Interlocking
Crystalline Interactions
Thermoplastic Structural Composite Materials
10. PROCESSING SCIENCE AND MANUFACTURING
TECHNOLOGY
Processing Science
Chemical Change
Thermophysical Properties
Rheology
The Analysis of Processing Operations
Manufacturing Technology
Consolidation
Continuous Consolidation
Tape Placement
Continuous Forming
Stamping
Diaphragm Forming
Incremental Processing
Machining
Assembly Technologies
Fasteners
Adhesive Bonding
Solvent Bonding
Fusion Bonding
Interlayer Bonding
Rework, Repair and Reclaim
Quality in Processing
11. DIRECTORY
Raw Material Suppliers for Plastic and Plastic Products
Manufacturers of Plastic Processing Machinery
Plastics Processing Machinery and Equipment (Foreign)
Machinery and Equipment for Plastic Converting
Extruders and Extrusion Lines
Injection Moudling Machines
Presses and Accessories
Blow-Moulding and Thermoforming Machines
Machinery for converting Reaction Resins
(Unsaturated Polyesters, Epoxies)
Coating Lines
Other Plastics Convertising Machines
Miscellaneous Plastic Machineries

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Sample Chapters


(Following is an extract of the content from the book)
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Properties and Applications of Thermoset Plastics

1.Phenol-Formaldehyde (PF)

Polics are thermosetting resins which are typically stiff and brittle. Phenolic resins were first tigated in the 1880s by Otto Bayer. In 1909, Dr. Bakeland produced the first commercial phenolic ing compound. But it was Harry H Dent founder general Plastics, who in 1921 developed the first nuous process for making phenolic moulding pounds. Phenolic resins are manufactured by plining phenol and formaldehyde. Two types of polic resin namely resols and novolaks are manuactured. Resol refers to a phenolic resin made acting 1.2 to 1.5 moles of formaldehyde with one of phenol in basic medium. Novolak is the resin the by reacting 0.8 mole of formaldehyde with one of phenol in acidic medium. The approximate tures of resols and novolaks are shown below:

Characteristics

  • Hard, stiff & brittle
  • Notch sensitive
  • Good retention of properties at elevated temperatures
  • Impact strength reduces with increase in rigidity
  • Excellent creep resistance
  • Good ageing properties
  • Excellent flexural fatigue resistance
  • Heat resistant
  • Good dimensional stability
  • Does not melt or soften on exposure to heat
  • Very good shear strength
  • Unaffected by hydrocarbons, oils, salt water, soap and detergent solutions
  • Good resistance to staining
  • Good insulation properties
  • Attacked by strong mineral acids & bases
  • Easy to mould
  • Excellent ability to be moulded to close tolerances.
PropertiesValues
Specific gravity1.40
Tensile strength, MPa48.3
Tensile modulus, MPa8276
Flexural modulus, MPa7042
Elongation at break, %1
Impact strength, izod, notched, J/m16.5
HardnessE85
Deflection temperature under load (1.82 MPa),°C 150
Coefficient of linear expansion mm/mm/°C39 x 10-6
Water absorption, 24 hours, %0.50
Dielectric strength, KV/mm8.87
Dielectric constant, 106Hz5.5
Power factor0.06
Volume resistivity, Ohm.m109 - 1013

Phenolic resins are available in the following grades:

  • General-purpose grade
  • Heat resistant grade
  • Impact modified grade
  • Glass filled grade
  • Mineral filled grade
  • Cellulose filled grade

Phenolic resins can be processed by the following techniques:

  • Compression moulding
  • Transfer moulding
  • Thermoset injection moulding
Manufacturers/SuppliersTrade Names
Fiberite Corpn.Fiberite
Union carbideBakelite
ToshibaTecolite
SterlingSternite
Allied ChemicalPlaskon
BP ChemicalCellobond
General ElectricGE-Genal
MonsantoResinox
Synthetic resinsUraver
Dynamit NobelTrolitan
Budd ChemicalPolychem
Plastic EngineeringPlenco
Tipco Polymers Pvt. Ltd.Tipcolite
Bakelite Hylam Ltd.Bakelite
Indian Plastics Ltd.Florite

Applications

Appliances: Iron-handles, domestic utensils, heat proof buttons, bottle closures, novelty items, mixie bases, cooking range parts, tube bases, boiler and panels, steam irons, coffee pot bases & handles, knobs, washing machine agitators, toaster ends, phonograph records, coatings for metal cans, refrigerator controls, window tracks, particle boards, glues, laminating wood and water outlets.

Miscellaneous: Bathroom fixtures, toilet seats, dinner wares, cooking range parts, rubber tackifer, butyl rubber curative, fibre glass & paper impregnation, foundry hot box, textile impregnations and X-ray shields.

Automotive: Auto coil tops, disk brake pistons, disconnect boxes, propellers, break linings, shell modelling, brake liners, gear, clutch disks, push buttons, lamp sockets, ignition parts, castor wheels, thrust washers, spacers, converter reactors, car instrument panels, speedometer housings, solenoid covers, commutators for window lights, bus bar supports, engine blocks and intake manifolds.

Electrical/Electronics: Fuse boxes, holders, connectors, lamp sockets, heat resistant lamp holders, fan regulator covers, rotary switches, circuit breakers, HRC fuses, telephone handsets, cyclostyling drums, relay base covers, power transmission components, insulators, pumps, automatic transmission reactors, dielectric housings, power train components and terminal blocks. Industrial/Mechanical: Water pumps, pulleys, calibration in circuit breakers, propellers, grinding wheels, bobbins and sleeves, rice rollers, carbonless copy paper, adhesive paints, tool handles, industrial items, textile components, textile drums, welding torches and picker bushes.

2. Amino Plastics

Urea-formaldehyde (UF) and Melamine-formaldehyde (MF) are called as amino plastics. These resins are derived from ammonia and hence they are referred as amino plastics. Urea formaldehyde was first produced in 1920s by Kurt Ripper & Firtz Pollac in Germany. Urea formaldehyde was commercialised in the year 1932 in America by the American Cyanamid Co. Melamine formaldehyde was commercialised in 1939 at American Cyanamid Co. When Urea or melamine is reacted with formaldehyde a clear thermosetting resin of urea formaldehyde or melamine formal dehyde is produced.

Characteristics

  • Stiff & brittle in nature
  • Hardest of all plastic materials
  • High modulus of elasticity
  • High mechanical strength and wear resistance
  • Free from taste and odours (compatible with foodstuffs)
  • Good electrical properties
  • No tendency to yellowing
  • Can withstand low temperatures without embrittlement
  • Good impact strength
  • Continuous use temperature for urea is 77°C and for melamine it is 99°C
  • UF & MF retain their properties even at 100°C and 130°C respectively.
  • Provides good surface durability and hardness
  • Good torque retention
  • Break resistant and chip resistant
  • Possesses good rigidity and load bearing strength
  • Resistant to organic solvents, oils, greases and fluorinated hydrocarbons
  • Melamine possesses good stain resistance and freedom from yellowing
  • Long-term oxidation resistance is poor
  • Very hard and scratch resistant
  • Melamine is waterproof in nature
  • Self extinguishing
  • Good colourability
  • Translucent to opaque in nature
  • Resistant to gasoline, acetone and detergents
  • Melamines are resistant to acids and alkalies and can withstand boiling water
  • Attacked by strong acids and bases
<td colspan='2' align='center'>Values
Properties
UF MF
Specific gravity1.5 - 1.61.5 - 1.55
Tensile strength, MPa52 - 8055 - 83
Tensile modulus, MPa9000 - 11000 11000 - 16500
Flexural modulus,Kg/cm2 x 102105.06 77.52
Elongation at break, %[11.6 - 2.4
Impact strength, izod, notched, Kg/cm/cm1.36 - 2.181.31 - 7.62
HardnessM 110 - 120M 115 - 125
Deflection temperature under load (1.82 MPa),°C 125 - 145175 - 200
Coefficient of linear expansion, mm/mm/°C2.5 x 10-54 x 10-5
Refractive index1.54 - 1.61.58 - 1.6
Dielectric strength, KV/mm1412
Dielectric constant, 60 Hz7 - 9.57.9 - 9.5
Power factor0.035 - 0.0430.03 - 0.083
Volume resistivity, ohm.cm 1-2 x 1012 1012 - 1013

MF is available in the following grades:

  • Moulding grade
  • Filled grade (cotton fibre and wood flour)
  • Glass filled grade
  • Alpha cellulose filled grade
  • Coating grade
  • Adhesive and bonding grade
  • Laminating grade

UF is available in limited grades than MF:

  • Moulding grade
  • Filled grade (cotton fibre and wood flour)
  • Alpha cellulose filled grade

Both UF and MF can be processed by the following techniques:

  • Compression moulding
  • Transfer moulding
  • Injection moulding
Manufacturers/SuppliersTrade Names
Urea Formadehyde
Allied chemicalsPlaskon
BASFBasoper
BIPBeetle, Mouldlite
MonsantoResimene
SterlingSternite
Nuchem Plastics Ltd.Presrite
Melamine Formaldehyde
Allied chemicalsPlaskon
American cyanamidCymel
BIPMelamex
Dynamit NobelUltrapas
MonsantoResirnene
Plastics EngineeringPlenco
Indian Plastics Ltd.Florite

Applications

Melamine Formaldehyde

Adhesives: Plywood bonding agents, laminating resins, paper resins and surface coatings.

Household: Dinner wares, cutlery handles, large serving utensils, bowls, trays, dispensers, ash trays, buttons, soap dispensers, vertical wall surfaces, furniture, bathroom wash basins, toilet seats, shower housings, door knobs, appliance components, coffee makers and flooring seats.

Electrical: Electrical parts, switch gears, welding rod holders, terminal strips, watt meter blocks, connector plug inserts, electrical panels & parts and printed circuit boards.

Miscellaneous: Boat hulls, powder bowls, school desk tops and flame boards.

Urea Formaldehyde

Electrical: Wiring devices, circuit breakers, wall plates, electric blanket control housings, plugs, sockets, holders and bed switches.

Miscellaneous: Closures, receptacles, toothpaste tube inserts, buttons, toilet seats, knobs, adhesives & bonding agents, flooring, furniture, binders for foundry cores, coated abrasive papers, foams, orthopedic casts and bandages.

Appliances: Hair dryers, food mixers, coffee percolators, table mats, telephone sets and cookware handles.

3. Epoxy Resins

Chemically, the term "epoxy" means a three membered ring containing one oxygen and two carbon atoms.

The molecules of 'epoxy resins are low in molecular weight and when cured they are joined together to form large cross linked structures. These final products are thermosets. Epoxy resins were first developed in 1930s in Germany. But the material was commercialised in 1946. Epoxy resins are manufactured by reacting polyhydric alcohols with epichlorohydrin. The largest produced epoxy resin called Diglycidyl Ether of Bisphenol-A (DGEBA) is produced by reacting bisphenol-A with epichlorohydrin.

Epoxy resins are cured with different curing agents like amines, amides, acids, acid anhydrides and amine aducts. Also, they are catalytically cured using tertiary amines. By selecting a suitable resin and a curing agent we can get a range of properties for different applications.

Characteristics

  • Good mechanical strength and dimensional stability
  • Good heat and chemical resistance
  • High dielectric strength
  • High strength and modulus
  • High volume resistivity
  • Good wear resistance
  • Excellent adhesion to wide range of materials
  • Excellent weatherability
  • High temperature resistance
  • Good Hardness, toughness and rigidity
  • Excellent corrosion resistance
  • Low curing shrinkage
  • Resistant to solvents
  • High heat distortion temperature
  • Low dissipation factor
  • Outstanding arc and tracking resistance
  • Flame retardant
  • Resins are highly viscous
  • Low potlife and shelf life
  • Poor oxidative stability
  • High cost
  • Susceptible to U V radiation
PropertiesValues of DGEBA
[/td Colspan=3 align=center]Cured with
Aliphatic polyamines Aromatic polyaminesPolyamides
Tensile strength, MPa40-708335-55
Flexural strength, MPa104-124152 48-62
Compressive strength, MPa138-227207 62-76
Dielectric constant at 50 Hz and 25°C4-5 4-53.2-3.6
Volume resistivity at 25°C, Ohm.cm1016 10161016

Some of the commercially Important epoxy grades are:

  • Diglycidyl ether of bisphenol-A resins
  • Epoxy - Novolac resins
  • Cycloaliphatic epoxies
  • Halogenated resins
  • Flexibilising diepoxides.

Epoxy resins can be processed by the following techniques:

  • Hand lay up and spray up techniques
  • Casting
  • Filament winding
  • Pultrusion
  • Impregnation and
  • Lamination

Applications

Adhesives: Metal to metal, non metallic surfaces, binders for industrial, seamless thin-set terrace flooring, concrete repair, ground water proofing membranes, decorative walls, light metal window & door frames, metal letter boxes, sheet metal laminates, pipe and hose coupling.

Automotive: Doors, seats, luggage carriers, wall linings for railway coaches, buses & ships, defrosting equipment for aircraft, fuel tanks, partition walls and body parts.

Casting: Battery casings, centrifugal pumps, pipes for liquids, flange coupling, closings, lab equipments and dye baths.

Electrical/Electronics: Low current applications, telephone & high frequency applications, x-ray apparatus electrical measuring instruments, transformers, rotors, circuit breakers, cable closing sleeves, cable and stoppers, inserts for switches, slot keys and encapsulation of pace makers.

Household: Coatings for drums, cans, washing machines and refrigerators, floors and repair kits.

Industrial: Lamination for drill jigs, router jigs, cutting, wrapping & welding fixtures, model core boxes, casings, coatings for metal sheet industry, machinery, containers pipes exposed to highly corrosive environments, chemical resistant pumps, pipes and impellers.

Roads and Highways: Test strips, sealing membranes, high friction surfaces, cast traffic reflectors, bonding new concrete to old concrete, reflection strips and traffic bars.

Sports: Skis, high jump poles, fishing rods, hockey sticks and drum sticks

Miscellaneous: Pottery moulds, press and vacuum forming tools, core boxes, moulds for RIM, laminates for aircraft and automobile components, laboratory bench tops, floorings, road surfacing, radiator supporters and transmission supporters.

4. Unsaturated Polyester Resins

Unsaturated polyesters are very versatile materials. They can be rigid, resilent, flexible, corrosion resistant and weather resistant. These resins were first synthesised in the year 1936 by Carleton Ellis and commercialised in 1941.

Unsaturated polyesters are usually manufactured by batch process. They are the condensation products of unsaturated dibasic acids (usually maleic anhydride), saturated dibasic acids and glycols. The glycols used may be ethylene glycol, propylene glycol or diethylene glycol. Important saturated acids used are phthalic anhydride and m-phthalic acid. The most common cross linking monomer used is styrene but vinyl toluene, methyl methacrylate and diallyl phthalate can also be used. Structure of Isophthalic acid polyester resin is given below:

Characteristics

  • Can be made rigid, resistant, soft or flexible
  • Can be made flame retardant, weather resistant and corrosion resistant
  • Cured resins are rigid and do not flow on heating
  • Resistant to yellowing on exposure to UV light
  • Attacked by alkalies
  • Good resistance to burning and ignition
  • Good heat resistance
  • High stiffness and impact strength
  • Low tooling costs
  • Poor abrasion resistance
  • Weak solvent resistance
  • Poor fatique resistance for flexible cast polyester resins
  • Laminates, SMCs and DMCs are very good in strength

Typical values of polyester hand lay up laminates

Manufacturers/suppliersTrade Names
Allied ChemEpiall, Plaskon
Union CarbideBakelite
DowchemDEN; DER
EpoxyliteEpoxylite
FiberiteFiberite
General ElectricArnox
ShellEpikote
BayerLekutherm
TufnolTufnol
SIP ResinsEpoxite
Ciba-Geigy India Ltd.Araldite

Unsaturated Polyester resins are available in the following grades:

  • General purpose grade
  • Flexible grade
  • Low shrinkage grade
  • Weather resistant grade
  • Chemical resistant grade
  • Fire resistant grade
  • Filled grade

Unsaturated polyesters can be processed by the following techniques:

  • Hand lay up and spray up techniques
  • Preform moulding
  • Centrifugal casting
  • Pultrusion and filament winding
  • Matched metal die moulding
  • Injection moulding and
  • Compression moulding for SMCs and DMCs
PropertiesValues
Tensile strength, MPa8 - 17
Flexural strength, MPa10 - 20
Flexural modulus, MPa3440
Power factor 106Hz0.02 - 0.08
Dielectric constant 106Hz3.2 - 4.5
Water absorption, %0.2 - 0.8
Manufacturers/SuppliersTrade Names
ArmcoArmco
BASFPalatal
BIPBeetle
BayerLegural
Freeman chemicalsFreflow, Flomat
Good yearVituf
ICIMelinex, Atlac
Rohm & HaasPeraplex
ShellEpocryl

Applications

Building & Construction: Building panels, cultured marbles, beams, water tanks, skylights, outdoor structural panels, fume hoods, play ground equipments, room dividers, roofing, siding, tanks, pipes and corrugated paneling.

Automotive: Automobile structural parts, auto body putty, aircrafts, safety helmets, guards, gelcoats, automobile springs, truck cabs, truck feners, recreational vehicles, automobile exterior parts and auto patching compounds.

Electrical/Electronic: Switch gear parts, fuse holders, street light housings and electrical components.

Household: Bathtubs, laundry tubs, septic tanks, trays, shower stalls, picture frames, appliances, buttons, furniture and tool boxes.

Industrial: Reaction vessels, tanks, large diameter pipes, mine bolts and castings.

Sports: Golf club shafts, archery bows, bowling balls and swimming pools.

Miscellaneous: Fishing rods, train interior components, boats, flag poles, glass fibre reinforced cycle parts and park benches.

5. Polyurethane

Polyurethanes are a wide variety of polymers with quite different compositions and correspondingly different properties. The characteristic structural element of almost all of these polymers is the urethane group formed in the course of polyaddition. In 1937, Otto Bayer and co-workers discovered the diisocynates addition polymerization that resulted in the preparation of many different types of polyurethanes. Although such polymers can be formed by a number of different chemistries, the most common method is by the reaction of a polyisocyanate with an organic polyhydroxy material (Polyol).

Polyurethanes are the most important class of polymers playing a vital role in many industries from ship building to footwear; construction of cars. They appear in an astonishing variety of forms. The various types of unsaturated polyurethanes are foams (Low density flexible foams, low density rigid foams, high density rigid foams), solid polyurethanes, adhesive, binders, coatings and paints. Plastics as such are harmless and environmental friendly. Among the various waste management options, plastics recycling is more ecofriendly and energy saving. Mechanical recycling is widely adopted in India ever since the manufacturing of plastic raw materials. Due to economic reasons recycled plastic materials find various applications from small gem clips to large pallets.

In general, polyurethanes are addition polymers manufactured by the reaction of di-or poly-isocyanates with polyols.

The reaction is exothermic. The rate of the polymeriation reaction depends upon isocyanate and the polyol.

In addition to isocyanates and polyols a wide range of chemicals may be added to control and modify both the polyurethane reaction and the properties of the final polymer. They include:

  • Catalyst
  • Chain extenders
  • Crosslinking agents
  • Surface active materials
  • Flame retardants
  • Colourants and
  • Fillers

Characteristics

Polyurethanes have found wide application in virtually every industry because of their characteristic general properties, the most important of which are :

  • High elasticity over the entire hardness range
  • Flexibility over a wide temperature range
  • Good weather resistance
  • Good resistance to oil, grease and many solvents
  • Excellent wear resistance
  • High Young's modulus compared with rubbers of a similar hardness
  • Performance above its Tg
  • Ability to stretch and retract instantly
  • Negligible crystallinity
  • Change in length in response to constant stress at variable temperatures
PropertiesValues
Tensile strength, Psi10,000 - 11,000
Elongation, %3 - 6
Flexural yield strength, Psi19,000
Hardness, Rockwell30-35
Flexural elastic modulus, Psi x 1066.1
Heat deflection temperature, °F190-200
Dielectric constant, 60 cyc 3.4 - 3.5
Dissipation factor0.008

Themoset polyurethanes are available in the following grades:

  • Foam grade
  • Elastomer grade
  • Coating grade

Themoset polyurethanes can be processed by the following techniques:

  • Casting
  • Reaction injection moulding (RIM)
  • Reinforced reaction injection moulding (RRIM)
  • Foam moulding
Manufacturers / SuppliersTrade Names
Stainffer Chemical Co.Everlon
Accessible Products Co.Acoustzip
Freeman Chemical CorporationChempol
American Cyanamide Co.Adaphah
Urethane Products Canada Ltd.Flexi-cast
Eagle picher Industries, Inc.Chem-Thane
N.L. Industries, Inc.Alfa
Upjohn Co. Castethane
Arveta, S.A.Avetone
Mobay Chemical Corporation Desmocoll
Bee Chemical CoBeethane
PPG IndustriesDurathane
North American Urethanes, Inc.Elastolur
Pan Chemical CorporationFawthane
Texaco Inc.J. Thane

Applications

Construction: Wall panels and roof tops, wall insulation, insulation of pipes and tanks, foam in place fox holes, soft hammers, pump housing, linings, friction drives and belts, pipe seals, spray protective layers and sealants.

Sports: Shoe heels & soles, handles for tennis rackets & golf clubs, golf balls, foot ball studs and shock-absorbing pads.

Automotive: Seating, interior padding, exterior body panels, complex soft front ends, components mounted in the engine space and accessories, cast tires, suspension systems, spring matting, bumpers, fenders, cushion and steering wheels.

Furniture: Cushion, mattresses, refrigeration insulation, refrigerated trucks and trailers insulation.

Miscellaneous: Engine parts & electronic tubes packaging, radios, wing tips in aircraft, fuselage insulation, blood oxygenator equipment, adhesive, coating metals, gaskets, bushings and switches.

6. Silicones

Silicones may be defined as synthetic compounds containing alternating silicon-oxygen backbone. This inorganic backbone is chemically modified with pendant organic groups to add flexibility and reactivity. Modern developments in silicone chemistry have sprung from Kipping's researches.

Silicon is manufactured by the reduction of silicon dioxide in electric furnaces. The elemental silicon is reacted with gaseous methyl chloride in the presence of copper catalyst to provide methyl chlorosilanes which are fractionated and the resultant dichlorodimethyl silane is hydrolysed with water to form linear and cyclic poly siloxanes.

Polyorganosiloxanes are normally referred to as 'silicones' and are polymeric substances with the structure given above. A wide variety of silicone resins are available commercially. The properties of the individual types differ somewhat depending upon the use for which they are designed. Silicones form the basis of a wide range of industrial products which may commercially be classified as fluids, resins and elastomers or rubbers.

Silicone forms

Silicone Fluids

A large number of silicone fluids have been synthesised and studied. Dimethyl silicone fluids and other silicone fluids belong to this category.

Silicone Resins

They are highly branched polymers that cure to solids

.

Silicone Elastomers

These are based on linear polymers of very high molecular weight which are analogous to the silicone fluids. Mechanical strength is imparted by the addition of suitable inorganic fillers and elastic properties are obtained as a result of intermolecular cross linking in the presence of an oxidising curing agent.

Silicone elastomers are manufactured in several forms: heat-cured rubber, liquid injection moulding elastomers, one-component room temperature vulcanizing sealants (RTV), two component RTV products and speciality fluorosilicones.

Characteristics

Silicone fluids

  • Transparent to visible light and UV radiation
  • Low pour point
  • High temperature stability
  • High compressibility
  • General inertness
  • Relatively constant viscosity over temperature
  • Unstable towards concentrated mineral acids

Silicone Resins

  • They resemble glass but are somewhat softer and usually soluble in solvent until cured.
  • Degree of hardness depends on the extent of cross linking
  • Very good heat resistance
  • Highly water-repellant
  • The resins are good electrical insulators particularly at elevated temperatures and under, damp conditions.
  • Have good resistance to most aqueous chemical reagents
  • Good inherent weatherability
  • Resistance to many organic solvents is poor

Silicone Elastomers

  • Degree of hardness depends on the extent of cross linking
  • Good resistance to most aqueous chemical reagents
  • General inertness
[tsble] PropertiesValues Silicone fluids (Dimethyl Siloxane 100 mol %) Viscosity at 25°C, mm /s10 Pour point, °C-73 Flash point, °C210 Thermal conductivity at 65°C,w/m K1.3 Electrical strength, KV/mm1.4 Electric constant2.6
PropertiesValues
Silicone impregnating resins
Wt. loss after 3 hrs. at 250°C, %4
Power factor at 25°C at 100 Hz0.0084
Dielectric constant at 25°C at 100 Hz3.0
PropertiesValues
General purpose silicone rubbers
Tensile strength, 1 bf/in500-1000
Hardness40-50
Useful temp., °C -55-250
Linear shrinkage, % 2-6
Power factor, 60 Hz0.002
Dielectric constant, 60 Hz3-6

Silicones are available in the following grades:

  • Resin grade
  • Elastomer grade
  • Rubber grade
  • Fluid grade
Manufacturers/suppliersTrade Names
Wacker -ChemieWacker, Elastosil
Union Carbide Corpn.Bakelite
Mobay Chemicals Co.Baysilone
Dow corning Corpn. Dow corning, Sylgard
Genera, Electric Co.G.E.
Crucible Chemical Co., Inc.Cru-Rez
Custom Materials, Inc.Custom - Load
Rhodia, Inc; May & Baker Ltd.Rhodorsil
SWS Silicones, Inc.Silgan
Textron Inc.Spenkel
Thiokol CorporationSpraythane
Thuscon laboratoriesSuper-Porseal

Applications

Silicone fluids

They are used in vinyl polishes and high temperature greases. Their most important application in relation to the plastics industry is as mould release agents. They are used as additives in polishes and waxes, heat-transfer fluids, electrical transformer fluids, textile fibre lubricants, antifoaming agents in chemical processes & carriers and softness in cosmetics.

(b) Silicone Resins

Silicone resins are employed in a wide and increasing range of industrial applications. These include surface coatings, high temperature paint additives, electrical moulding compounds, masonry water repellants, abrasion resistant coatings for plastics, tackifiers for silicon adhesives and for electrical applications.

Abrasion resistant silicone coatings are used to protect transparent plastics against scratches, chemical attack and UV degradation. Silicone is widely used as the release coating on plastic film label stock.

The use of silicone resins in paints and other surface coatings depend on their heat resistance, water repellency and resistance to chemical reagents. A blend of silicone and organic resins pigmented with aluminium powder is used in applications such as coatings for metal chimneys, exhaust pipes and furnace doors involving exposure to temperatures upto 500°C.

Silicone resins form useful release agents and although more expensive initially are more durable. To release confectioneries from baking pans, these resins are used.

Silicone laminates are used in electrical applications such as slot wedges in electric motors, terminal boards, printed circuit boards and transformers.

Silicone Elastomers

Made into parts like valve cover, oil pan gaskets, device axle boots, o-rings, diving masks, medical catheters, hose, tubing, wire and cable, sponge & profile, tiny and complex parts, electrical connectors and baby bottle nipples. Adhesives, sealants and many industrial grades are used for glazing and for gaskets.


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